[1193] PET-CT Imaging in Lesions of the Tonsil for the Detection and Staging of Squamous Cell Carcinoma: A 3 Year Experience in 43 Cases.

Ramya P Masand, Guocheng He, Peeyush Bharagava, Linda K Green. Baylor C. of Med. and ME DeBakey VAMC, Houston, TX

Background: Positron Emission Tomography-Computerized Tomography (PET-CT) has a role in the staging of head and neck (H&N) squamous cell carcinoma (SCCs). In the pharyngeal palatine tonsil (PPT), it has been reported that there may be up to a 40% false positive rate. In the PPT, the calculated standardized relative uptake values (SUVs) on PET-CT is 3.48 +/- 1.3 in normal patients. It is reported that an SUV difference between right and left of 0.83 or > will pick up 100% of occult SCCs.
Design: We searched our files for tonsil biopsies performed since 2005. We reviewed the clinical, radiographic, pathologic findings. PET-CT was performed in selected patients using 18F-FDG PET fused with a low dose non-contrast CT scans. The tonsil location SUVs were recorded and compared to pathologic data. Other sites of increased SUV uptake were also recorded.
Results: There were 901 patients with tonsil histology. There were 43 patients with PET-CT scans. The SUV values in the PTTs ranged from 0 to 35. There were 19 biopsy negative cases which showed either reactive hyperplasia or atrophy (Table 1). All cases with SCC in the H&N region were diagnosed prior to the PET-CT scan via tonsil biopsy or biopsy of a another site (lymph node or another H&N location). No occult SCCs were found with PET-CT. There were 2 cases (SUV 0) in which the biopsy showed SCC. SUV values between the right and left tonsils did not predict cancer. The patients with SCC SUVs ranged from 0-35 and patients without SCC ranged from 2.8-8.2 (Table 1). Over 33% of patients with a high SUV on PET-CT had no SCC at tonsil biopsy. In tonsil SCC, there was a false negative rate of 35%.

Table 1: SUV to Tonsil Biopsy Diagnosis
SUV numberTonsil with SCCTonsil Negative
Normal range87

Conclusions: PET-CT is useful in the diagnosis, staging and prognosis of H&N SCC but is not as useful in PPT sites due to inherent lymphoid tissues that may be atrophic or reactive with varying SUVs. An extremely high SUV (>8) may be of value but SUVs of 3-8 may be fraught with false positive and false negative diagnoses. It should be known that occult squamous cell carcinoma may have no SUVs and biopsies in patients with metastatic SCC in the neck should have all locations in the H&N biopsied despite PET-CT findings of low values. It has been our experience that 100% of our patients without known biopsy proven SCC in the H&N regions had only reactive lymphoid tissue at PTT biopsies directed by PET-CT.
Category: Head & Neck

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 140, Tuesday Afternoon


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